SRV-06

Differential levelling rise

Δh = BS − FS on a level line.

Reading speed

LevellingISO 17123-2

Governing equation

\Delta h = \mathrm{BS}-\mathrm{FS}

where

BS: Backsight (m)
FS: Foresight (m)
\Delta h: Rise (m)

Lecture brief

Historical brief

From chain and theodolite through Bowditch’s compass-rule (1802) to GPS PDOP, surveying is the propagation of small errors across a network. These sheets close traverses, reduce stadia and state map scale. This sheet (SRV-06 — Differential levelling rise) is the form associated with ISO 17123-2. Working symbols: $BS$ , $FS$ $\rightarrow$ $\Delta h$ . A collimated horizontal line of sight intercepts two staves; the difference of readings is the rise of the ground.

Purpose

Purpose: compute

\Delta h

from

BS

FS

in Surveying via

\Delta h = \mathrm{BS}-\mathrm{FS}

Δh = BS − FS on a level line. Use it when a real surveying question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

BS = 1.456\,\mathrm{m}

FS = 1.208\,\mathrm{m}

, the governing relation

\Delta h = \mathrm{BS}-\mathrm{FS}

yields

\Delta h = 0.2480\,\mathrm{m}

. Single setup, no collimation or curvature correction. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Backsight BS1.456 mForesight FS1.208 m

Outputs

Rise \Delta h0.2480 m

Reading speed

Watch on YouTube

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Narration of this film

Single setup, no collimation or curvature correction.

A collimated horizontal line of sight intercepts two staves; the difference of readings is the rise of the ground.

Reading speed

Watch on YouTube